As is known, cathode ray tubes (CRT), such as used in television receivers, commonly generate undesired large transient voltages within the tube. Such voltages must be controlled and dissipated in order to avoid conduction of these high voltages through the tube pins and tube socket contacts to other portions of the circuitry associated with the tube; otherwise, these large voltages may damage the tube and the tube terminals, and may also couple to, and damage, the associated electronic circuitry.
Such large voltage transients may be due to arcing, which is a result of the ionization and breakdown of air or other gas media between two or more points of high potential difference. When arcing occurs, this excessive high voltage transient over-stresses the picture tube, high voltage components and wiring, which may damage the tube and associated circuitry.
In order to dissipate the excessive voltages, CRT sockets are normally provided with some type of safety device, in the form of a grounding apparatus. Thus, in the event that a particular pin has an excessive potential impressed thereon, the grounding apparatus permits a spark to jump, or arc, from the pin contact to ground. The foregoing prevents damage due to excessive potential at the particular pin by providing non-destructive path to ground, to thus eliminate the over-voltage.
In addition, various tube leads must be operated at different potentials in order to perform the desired function. Further, the potential to the leads should be adjustable to compensate for variations in the desired voltage. Such variations may be due, such as for manufacturing tolerances or various environmental conditions, including varying supply voltages. Most frequently, the voltages that must be controlled are the focusing voltage coupled to the first grid (G.sub.1) of the CRT, and a second voltage coupled to the accelerating grid (G.sub.2) of the picture tube.
Heretofore, in the prior art, sockets have been built to provide the spark or arc gap apparatus and to provide an adjustable voltage feature, as, for example, in U.S. Pat. No. 3,251,016 to Manetti, et al., and assigned to the same assignee as the present invention. Other devices are known, which have included the positioning of a printed circuit board adjacent to the CRT socket.